It is known in the art, as disclosed in Japanese Patent Publication No. S58-32908, that an oil separating device is provided in a Rankine apparatus. A heat exchanger is provided in the oil separating device for supplying heat energy into an oil pooling portion, so that refrigerant melt in lubricating oil is vaporized. Then, the lubricating oil having a smaller amount of the refrigerant is supplied to an expansion device of the Rankine apparatus.
The above oil separating device is, however, independently provided from the expansion device. Accordingly, the structure for the Rankine apparatus becomes more complicated and connecting portions in the Rankine apparatus are increased. As a result, it is hard to apply the Rankine apparatus to a vehicle, in which mounting condition is strict.
Another fluid machine is known in the art, as disclosed in Japanese Patent Publication No. 2004-232492, in which a pomp-motor device (that is the expansion device, which is also used as a compressor) and an electric rotating device are integrally formed in a housing. According to the prior art fluid machine, the fluid machine is used such that an operating axis is arranged in a horizontal plane. A valve device is provided in the pump-motor device to switch over flow direction of working fluid, so that the pump-motor is operated either as the compressor device or as the expansion device. A low pressure port is provided in the housing at such a side position of the electric rotating device which is opposite to the pump-motor device. When the pump-motor device is operated as the expansion device, the working fluid discharged from the expansion device flows through the inside of the electric rotating device and flows out from the low pressure port.
The lubricating oil is generally mixed with the working fluid in the above fluid machine, so that sliding portions of the expansion device or the electric rotating device are lubricated by the lubricating oil. When the fluid machine is used in such a position that the electric rotating device is arranged at an upper side of the expansion device, the working fluid discharged from the expansion device flows from a lower side of the electric rotating device toward an upper side thereof, so that the working fluid flows out from the low pressure port. Accordingly, the lubricating oil is carried off from the low pressure port by the working fluid which is continuously discharged from the expansion device, even when the lubricating oil is separated from the working fluid within a space of the electric rotating device formed in the housing. Therefore, it is difficult to pool the lubricating oil at the lower portion of the space for the electric rotating device. Furthermore, the temperature of the working fluid at an outlet side of the expansion device is higher than that at an inlet side thereof. A larger amount of the working fluid is melt in the lubricating oil, to thereby decrease viscosity of the lubricating oil. As a result, a sufficient amount for a thickness of an oil film may be hardly obtained at the sliding portions.
According to another prior art, such as Japanese Patent Publication No. H5-79481, such a compressor or a pump device is also known as a fluid machine, according to which sucked working fluid is pressurized and pumped out. Namely, the compressor or the pump device of the fluid machine is a roller-type, wherein a roller (i.e. a cylindrical piston) is slidably provided on an eccentric shaft portion of a driving shaft, and the roller is moved in an orbital motion within a cylinder, so that the working fluid sucked into the cylinder is pressurized and pumped out. The lubricating oil is supplied to sliding surfaces between the eccentric shaft portion and the roller.
Both axial end portions of the eccentric shaft portion are formed as small diameter shaft portions, and annular seal members are provided at such positions, which are between an outer peripheral portion of a large diameter shaft portion and an inner peripheral surface of the roller and which are at both axial ends of the large diameter shaft portion, in order to prevent the lubricating oil from flowing into a working chamber of the cylinder. Small spaces are formed between the inner peripheral surface of the roller and the small diameter shaft portions, such that the small spaces receive a part of the working fluid leaking from the high pressure working chamber to a side of the sliding portions. At an initial stage of a suction stroke, the small spaces are communicated with a suction passage, so that the working fluid flows out from the small spaces into the suction passage.
In the fluid machine used as the liquid pump for circulating the working fluid in the Rankine cycle, it becomes harder to form the oil film at the sliding portions when the liquid phase working fluid of low viscosity flows into the sliding portions. Accordingly, it is necessary to supply the lubricating oil of the high viscosity to the sliding portions and to prevent the liquid phase working fluid from flowing into the sliding portions, in order to surely achieve good lubrication at the sliding portions.
When the above fluid machine is, for example, used as the liquid pump for such cases, it becomes possible to supply the lubricating oil of the high viscosity to the sliding portions and to prevent the liquid phase working fluid from flowing from the working chamber into the sliding portions.
However, the above fluid machine has a complicated structure, and therefore, it is a problem in increase of the number of parts and increase of assembling steps, when the small diameter shaft portions are formed at the eccentric shaft portion and annular grooves are formed at the large diameter shaft portion to provide therein the seal members.
Furthermore, another Rankine apparatus is known, for example, as disclosed in Japanese Patent Publication No. S59-138707. The Rankine apparatus includes a refrigerant pump, a steam generating device, an expansion device, and a condensing device, which are connected in a circuit. A bypass passage, which communicates an inlet side and an outlet side with each other, is provided at an outside of the refrigerant pump. A bypass passage closing device is provided in the bypass passage. A check valve is provided at the inlet side of the steam generating device, an expansion-side closing device is provided at the inlet side of the expansion device, and pressure detecting devices are provided at the inlet and outlet side of the expansion device.
In the Rankine apparatus, the expansion-side closing device is opened at starting up the Rankine apparatus. The bypass passage closing device is closed when a detected pressure difference obtained by the pressure detecting devices becomes higher than a predetermined value. The bypass passage closing device is opened when stopping the Rankine apparatus. The expansion-side closing device is closed when the detected pressure difference obtained by the pressure detecting devices becomes smaller than the predetermined value.
According to the above structure and operation, the pressure at a high pressure side and the pressure at a low pressure side are equalized by opening the bypass passage closing device provided in the bypass passage. A ratio of change of the differential pressure between the high pressure side and the low pressure side, for a unit time, is made smaller. As a result, a safer starting up and stopping operation is realized.
At the starting up operation of the Rankine apparatus, the working fluid in the steam generating device is in the liquid phase condition, because the working fluid is not yet sufficiently heated. Therefore, the liquid phase working fluid flows from the steam generating device into the expansion device. In the fluid machine like the above expansion device, lubricating oil is contained in the working fluid, so that lubrication is achieved at sliding portions in the expansion device by circulating the lubricating oil together with the working fluid. In the case that the working fluid is in the liquid phase condition, the viscosity of the lubricating oil is extremely decreased. As a result, sufficient lubrication at the sliding portions may not be achieved.
It is considered as effective to provide the bypass passage at the side of the expansion device, in order to equalize the pressure for the purpose of a safer operation of the Rankine apparatus and at the same time to solve the above problem. However, when the bypass passage is provided as in the apparatus of the above mentioned Japanese Patent Publication, a performance for mounting the apparatus in a limited space is deteriorated and cost for the bypass passage is increased, because the bypass passage is provided at the outside of the expansion device.